Ignore autogenerated mkheader binaries

Signed-off-by: Nasser Grainawi <nasserg@quicinc.com>
diff --git a/.gitignore b/.gitignore
index 1dcd62e..a0c5437 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@
 tags
 TAGS
 local.mk
+target/*/tools/mkheader